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Item level
The following text is an attempt to find the formulas used by Blizzard when creating items. It was originally posted by Hyzenthlei, Tauren Shaman 60 on Zul'Jin, in the Raids&Dungeons forums. Since good posts tend to disappear from the Blizzard forums sooner or later, I copied and edited it here. So far these calculations work reliably for most equipment. Terms and definitions *'StatValue' — the amount of a given stat on an item. *'StatMod' — the weighting given to a specific stat, this is how stats are compared in value. *'ItemValue' — the total value of the stats on an item. *'SlotMod' — weighting for adjusting the value of an item based on equipment slot. *'ItemSlotValue' — this is the ItemValue modified for the item slot. *'ilvl' — the effective level of an item (hidden in game). The minimum character level required to use an item is ilvl – 5 (capped at 60). Calculating Item Level This calculation is a three step process. First, the individual stats are each multiplied by their modifiers and taken to the 1.5 power, these terms are summed up and taken to the (2/3) power. The result, the Item Value, is a direct measure for the item's quality. It represents the feeling how "good" an item is. *ItemValue = [(StatValue1*StatMod1)1.5 + (StatValue2*StatMod2)1.5 + ...]2/3 / 100 Next, this sum is modified by the slot (or item type): *ItemSlotValue = ItemValue * SlotMod The final modification takes into account item quality. The end result is a calculated value for item level. *Green: ilvl = ItemSlotValue / 0.50 + 4.00 *Blue: ilvl = ItemSlotValue / 0.62 + 1.84 *Epic: ilvl = ItemSlotValue / 0.78 + 1.30 This calculated item level matches Blizzards item level quite well. A few remarks on the ItemValue formula: #It is quite simple, but not so simple that it is just all the stats added together. #Each stat is taken to the 1.5 power. This isnt too fast of a growth, but it does cause a single high stat to be weighted fairly heavily. For example, if we had two green leg items, one with +15 to a single stat and another +9 and +10 on two different stats, their calculated item levels would be 20.5 and 20.6. #After summing the series of stats to the 3/2 power, the total sum is taken to the 2/3 power, to keep the ItemValue scale linearly with the item level (not with a power). StatMods The numbers for StatMod were taken from a Blizzard slide on BlizzCon. It was revealed in this slide that 1% Melee Crit = 14 points, and 1% to Dodge = 12 points. The factors for the other modifiers were reverse-engineered from there. Due to the nature of the formula, an item of the same level can have more of a stat with a low stat mod, than with a high one. So for example 1% Crit = 14 Agility and 5 mana regen/5 = 12 Spirit. Notes: *''+Holy has value of 0.92 on some items (according to Hyzenthlei), while for example Green Lens will have the same +34-36 to any school including Holy'' *''+Weapon skill (daggers) - Possibly just due to having more examples, most other weapon skill mods have several clumped onto one item'' *''Magic Resist (All schools) includes items that specifically state "All Resistances", along with items that list each individual school. *''An item that adds damage to two schools of magic is only charged for one. Eg, Elemental Mage Staff, Robe of Winternight. It does not matter if a caster can use both schools or not. *''Some stat combinations are not allowed, for example strength and attack power. These stat mods were obtained by evaluating several thousands of items. Some values (esp. str, int, resists, +spell damage) are pretty reliable since they occur on many items and in large values. Knowing the base that Blizzard uses, most others can be rounded to a number that would appear to make sense, increasing accuracy. Some of these weightings seem to be different on different item types. A quick, probably non-conclusive quide follows: Slot Modifiers Some item types have better or more stats than items that go in different slots. Helms for for example will always give better benefits than bracers of the same item level. A high SlotMod (and consequently low SlotValue) in this table means that the item will have worse stats than an item for a slot with a lower number and the same ilvl. Weapons DPS Trade Neither casters nor feral druids benefit from weapon DPS. Thus some high end weapons may have some of their DPS sacrificed in favor of spell damage or feral attack power. A few melee weapons also do this, in favour of large damage procs. Two examples are Jeklik's Crusher, and Thunderfury, Blessed Blade of the Windseeker. SacrificedDPS = ilvl-60 Added Spell Damage and Healing = 4*SacrificedDPS Added School Spell Damage = 5*SacrificedDPS Added Spell Healing = 7.66*SacrificedDPS Added Feral Attack Power = 14 * (ilvl-60) Feral Attack Power is unique in that it doesn't cost any stats - nor dps, for example: Hammer of Bestial Fury Unique Main Hand 69 - 130 Damage (52.4 damage per second) 90 Armor +13 Strength +12 Stamina Requires Level 60 +154 Attack Power in Cat, Bear and Dire Bear forms only. Item Level 71 Expected DPS: 52.5 The Expected DPS and actual DPS match perfectly - the item is slightly over budget (iLvl 74), and the (71-60)*14=154 feral attack power is free. Notes: * Sacrificed DPS may vary by a bit either way. However (ilvl-60) generally works * Hyzenthlei suggests that Sacrificed DPS creates additional stat points which are spent in those stats. * For majority of high end weapons all those mods come only as a result of DPS sacrifice. Procs and uses effects The stat mods table contains the most frequently appearing stats. There are other stats which are sometimes unique or difficult to describe. All procs fall in this category, as do all Use: abilities. While these dont fit with an immediately obvious value, this system can be used to see what the blizzard item designers think they are worth and translate them into a stat-equivalent format. Armor Scaling Armor values on items follow a simple linear scaling pattern within certain limits. For example, mail armor scales linearly between certain ilvls, at which points the slope of the linear increase changes. One of these points is ilvl 45, above this point it scales more rapidly. Remember that an ilvl 45 item can be worn at lvl 40, and shamans and hunters get mail at 40. So they wanted mail to scale up fast for those classes, but without raising the amour values of pre 40 warriors too high (dont worry warriors, plate armor scales up even faster). An example of armor scaling is shown below. Green Plate Chest AC = (ilvl-44) * 8.9 + 428 The armor value of rare or epic pieces is also very easy to obtain using a simple multiplier. If you really want to go into detail, you will notice that there are plate chests with ilvls below 44. Due to their ilvl they should be equippable below lvl 40 (if any class could) and follow a different scaling equation (which is why jouster plate stuff has such pitiful armor values compared to many other starting plate item, their ilvls are all low). For Items of the same armor type (cloth, leather, etc) and the same ilvl *Rare Armor Value = Green Armor Value * 1.1 *Epic Armor Value = Green Armor Value * 1.2 The exception to this is shields, which use a slightly different scaling *Rare Shield Armor Value = Green Shield Armor Value * 1.125 *Epic Shield Armor Value = Green Shield Armor Value * 1.25 Of course there are items with much higher armor than others around that lvl. Those items are using the extra armor as an actual stat. Only this extra armor, above and beyond the predicted armor is considered in item weighting. So while the base armor level of an item is free, going higher will cost you other stats. The item slot plays a role in armor as well: Examples AC example To find an expected armorvalue for a given item you will first need to know the scaling of that item type. Do a search on thottbot for green items of that type, with lvl ranges of 44-46. Find the base armor they have. Then do the same for items of that slot at ilvl 61-63. Then use ArmorScaling = (higharmor - lowamor)/(highilvl - lowilvl) this is the armor increase per ilvl for a green of that armor type. Once you have that, do ArmorValue = (Desiredilvl - highilvl)*ArmorScaling + higharmor This will give the value of a green at that ilvl. Then multiply it by 1.1 for a rare, or 1.2 for an epic. Let's try this on a stormrage helm, 183 armor, ilvl 76. Green leather helms: ilvl 45, armor 99 ilvl 64, armor 132 ArmorScaling = (132 - 99)/(64-45) = 1.74 armor/ilvl (76 - 64) * 1.74 + 132 = 152.8 152.8 * 1.2 = 183.4 -> 183 armor You can use this to find the ArmorScaling factor and expected armor for any item. Item value examples Circle of Applied Force Binds when picked up Unique Finger Miscellaneous +12 Strength +22 Agility +9 Stamina Requires Level 60 Item Level 75 If we calculate the Item Value from the stats, we find that it's effective item level is 73.2. We can also try this on Cloak of the Shrouded Mists Binds when picked up Back 57 Armor +22 Agility +12 Stamina +6 Fire Resistance +6 Nature Resistance Requires Level 60 Item Level 74 This iLevel 74 epic cloak has an actual item value of 73.9. And just so you casters dont think Im forgetting you (Im a healer too after all). Shroud of Pure Thought Binds when picked up Back 57 Armor +10 Stamina +11 Intellect Requires Level 60 Equip: Increases healing done by spells and effects by up to 33. Equip: Restores 6 mana every 5 sec. Item Level 75 Here it slightly exceeds its item level, with an effective item level of 75.5. Item Creation Gone Wrong - Mislabelling The Drape of Benediction had its stats increased in a recent patch. Prior to that, it could be proven with this forumla that it was actually a blue item, mislabelled as purple. Since the patch, the drape is an epic worth its designation. A more recent example is the ironically much desired Eyestalk Waist Cord: Eyestalk Waist Cord Binds when picked up Waist 75 Armor +10 Stamina +9 Intellect Requires Level 60 Equip: Improves your chance to get a critical strike with spells by 1%. Equip: Improves damage and healing done by magical spells and effects by up to 41. Item Level 88 An epic of level 88, yet only has the stats of a 78. Proof: ((41*0.85)^1.5 + (1*14)^1.5 + (10*1)^1.5 + (9*1)^1.5)^2/3 = 46.466 46.466 / (0.777 = Waist Mod) / (0.7814 = Epic Multiplier) + (1.3 = Epic Offset) = 77.8 Another example is the Ironvine Belt. Ironvine Belt Binds when equipped Waist 408 Armor +12 Stamina +15 Nature Resistance Requires Level 60 Equip: Increased Defense +3. Item Level 70 Supposedly a blue of iLevel 70, it doesn't even have the stats of a level 70 green! ((12*1)^1.5 + (15*1)^1.5 + (3*1.5)^1.5)^2/3 = 22.848 As a blue, its effective level is: 22.848 / (0.777 = Waist Mod) / (0.62125 = Rare Multiplier) + (1.8375 = Rare Offset) = 49.2 And as a green: 22.848 / (0.777 = Waist Mod) / (0.5 = Rare Multiplier) + (4 = Rare Offset) = 62.8 This is currently the most underpowered item in the game. Items Valued with unnaturally high ItemValue There are also items that have been tweaked or changed by blizz that have item values far above what they should (and if you look carefully for discrepancies you will be able to tell which they are). But Im not going to go into specifics as I was asked by people who use them not to get them nerfed ;) Category:Formulas and Game Mechanics